Select the key blank materials

Screw material selection is the key to ensure the quality of screw, general requirements are: ( 1) Has good processability, grinding crack not easily, can get a good surface finish and smaller residual internal stress, a smaller effect on tool wear. ( 2) Tensile strength limit is generally not less than 588 mpa. ( 3) Good heat treatment craft, good hardenability, quenching crack not easily, homogeneity, the heat treatment deformation is small, can obtain higher hardness, thus ensuring the stability of the wear resistance and size of a ball screw. ( 4) Uniform material hardness, metallographic organization conform to the standard. Commonly used materials have: no hardened screw commonly used T10A, T12A and 45, etc. ; Hardened screw often choose 9 mn2v CrWMn, etc. 9 mn2v has good manufacturability and stability, but the hardenability is poor, often used in precision screw diameter of 50 mm or less; CrWMn steel after heat treatment has the advantage of small deformation, is suitable for making high precision spare parts, but its easy to crack, grinding technology is poor. The higher the hardness of a ball screw is wear-resisting, but manufacturing is not easy to grinding. Screw materials should have sufficient strength, a certain power to ensure that the transmission; Should have good heat treatment craft ( Good hardenability, small heat treatment deformation, not easy to crack) , and can obtain high hardness, good wear resistance. Screw nut materials commonly used GCrl5, CrWMn, 9 crsi, 9 mn2v, heat treatment hardness of 60 ~ 62 HRC. Overall quenching deformation is bigger, in the process of heat treatment and grinding technology is poor, should be used as surface hardening treatment. The ball screw for the 9 mn2v hot rolled round steel, quenched and tempered hardness is 250 HRS, in addition to the thread, the rest of the high frequency hardening 60 HRC. Material must be approved by spheroidizing treatment before machining, and inspected strictly according to the sample cutting. In order to eliminate the residual stress which is caused by the instability of the microstructure and arrange the cold processing, transformation of retained austenite after quenching martensite. In order to ensure the quality, blank after heat treatment in magnetic testing, to check whether there is micro crack parts.